OP: Your ranks aren't spectacular. Don't fret about your internal marks, they will be changed by the Board of Studies in a process called moderation. Try and perform extremely well in the externals, they will average out with your internal mark to produce a decent HSC mark. Good luck.
29. In how many ways can 4 people be accommodated if there are 4 rooms available? (answer = 256) <--- how come the answer isn't simply 4P4?
Each individual has 4 choices. Therefore there are 4^4 choices available. (fitzpatrick ay)